How to move multiple vertices like subdivide?
To move vertices precisely along edge normals, you can use an addon called Offset edges.
Installation
Once you download the addon, go to user preferences, install addon from file, and select the downloaded file. Then make sure to tick the chckemark button to enable the addon, and save user preferences.

Usage
Once you have it loaded, in edit mode, in the left-hand toolbar, there is a new sub-tab called offset edges. There are three commands - offset, extrude, and move. In your case, you would select the move command, after which you can specify the width.

A sidenote - it's best to model in quads whenever you can in order to be able to subdivide your geometry efficiently with loop cuts.